The present invention refers to a restriction valve device for hydraulic pressure fluids in vehicle shock absorbing mechanisms comprising a valve seat member with at least one main opening for the passage of said pressure fluid, said main opening being closable by means of a movable spring-biased valve body, and at least one auxiliary opening for the pressure fluid, said auxiliary opening being selectively closable by a closure element.
Restriction valve devices of this kind are previously known. As far as shock absorbers for vehicles and the like are concerned it is often desirable that the damping action obtained be variable so that the shock absorber can be adapted as requested to various requirements. As is known, the damping action of hydraulic shock absorbers is obtained by intentionally restricting the flow of the hydraulic liquid between various chambers to either side of a movable piston or the like by means of a restriction valve device. Most often a flow passage or a plurality of circumferentially spaced openings are closeable by means of a valve body which is spring-biased towards a closed position. By varying the number of openings and/or their crosssectional area, a flow resistance and hence a restricting action of desired, predetermined characteristics can be obtained.
Particularly when it comes to vehicle shock absorbers it is also desirable however, that the damping action be controllable. Almost without any exceptions this has been effected in prior art devices by exposing when desired one or more further flow passages for the hydraulic fluid by means of some further valve body or action. Common to these prior art structures is that they are very complicated and thus expensive and also that they are slow in their action. A vehicle shock however, should be capable of changing the restriction characteristics very fast, i.e. in a shorter time than 5 ms, and the arrangement employed should not be too power-consuming.
An example of prior controllable restriction valve device is disclosed in JP No. A 57 173629. According to said publication a solenoid-operated valve means is adapted to be pressed against the mouth of at least one of a plurality of hydraulic fluid flow passages through a piston. The flow area thus is reduced and the restricting action and hence the damping action increased.
Another example of a previously known adjustable restriction valve device is GB No. A 2 112 104. With the exception of the fact that the adjustment of the characteristics of the restriction valve device is obtained by angularly adjusting a member provided with flow passages so as to expose a greater or smaller number of flow passages, the basic operation in principle is the same as in the aforementioned Japanese publication. The restriction valve device of this British reference also utilizes electromagnetic actuation although not in connection with a real solenoid mechanism.
A further example of an adjustable restriction valve device in connection with the shock absorbers is EP No. A 0123365. This European publication discloses a double-acting hydraulic shock absorber having a restriction valve device comprising a control body which is also provided with a solenoid and adapted to effect, by energizing the solenoid, an axial displacement of a closure means in order to expose at least one further flow passage for the hydraulic fluid. As a result greater flow rates through the restriction valve device are provided for and hence a reduced or smaller damping action.